The Longitudinal Study of Australian Children
Annual statistical report 2010

1 Introduction

Children born in the early years of this millennium are growing up in an Australian society different to that experienced by any previous generation. In order to ensure that children growing up in Australia have every chance to experience a happy and healthy start to life, it is essential that policy-makers and researchers have access to quality data about children's development in the current economic, social and cultural environment. Growing Up in Australia: The Longitudinal Study of Australian Children (LSAC) is Australia's first nationally representative longitudinal study of child development. The study provides valuable data on children, their families and their wider environments, and enables researchers and policy-makers to understand how these change and interact as children grow up.

This is the first volume in the LSAC Annual Statistical Report series. The purpose of these reports is to provide an overview of the data from the study and thereby describe aspects of Australian children's lives and development. The reports will also be able to provide longitudinal statistics to describe the dynamics of change as children develop, and how their families and lives change as they grow older.

This report is structured around six themes (covering the two broad domains of children's environments and children's development), with chapters as follows:

1. Introduction

Families

2. Characteristics of the children and their families

3. How family composition changes across waves

4. Parents and the labour market

5. Parenting practices and behaviours

Education

6. Children's experiences of child care

7. Family education environment

Housing, neighbourhood and community

8. A longitudinal view of children living in disadvantaged neighbourhoods

Socio-emotional development

9. How young children are faring: Behaviour problems and competencies

Cognitive development and learning

10. Children's language development

Physical development and health

11. Children's pre- and peri-natal health experiences

Each chapter concludes with a list of "further reading" for those interested in other LSAC work undertaken on particular topics.

The first section of this introductory chapter provides a brief overview of LSAC and the second section describes the analytical approaches used throughout the main chapters.

1.1 About the study

Growing Up in Australia: The Longitudinal Study of Australian Children is Australia's first nationally representative longitudinal study of child development. The purpose of the study is to provide data that enable a comprehensive understanding of children's development within Australia's current social, economic and cultural environment (Department of Families, Housing, Community Services and Indigenous Affairs [FaHCSIA] LSAC Team, 2009). The longitudinal nature of the study enables researchers to examine the dynamics of change as children develop, and to go beyond the static pictures provided by cross-sectional statistics.

The study was initiated and is funded by the Australian Government Department of Families, Housing, Community Services and Indigenous Affairs and is conducted in partnership with the Australian Institute of Family Studies (AIFS) and the Australian Bureau of Statistics (ABS). A consortium of leading researchers and experts from universities and research agencies provide advice to the study.

Study design

The study has an accelerated cross-sequential design, with two cohorts of children:

  • the B ("baby") cohort, who were aged 0-1 years at the beginning of the study (born from March 2003 to February 2004); and
  • the K ("kindergarten") cohort, who were aged 4-5 years at the beginning of the study (born from March 1999 to February 2000).

The first wave of data collection was in 2004, with subsequent main waves every two years. Table 1.1 summarises the ages and sample sizes for the two cohorts across the first three waves of the study.

This design means that from the third wave of the study, the children's ages overlap. That is, children are aged 4-5 years in the first wave for the K cohort and in the third wave for the B cohort. In covering the first three waves of the study, this report includes data on children between the ages of 0 and 9 years.

Table 1.1 Number of children, B and K cohorts, Waves 1-3
  Wave 1 (2004) Wave 2 (2006) Wave 3 (2008)
B cohort 0-1 years 2-3 years 4-5 years
5,107 4,606 4,386
K cohort 4-5 years 6-7 years 8-9 years
4,983 4,464 4,332

Respondents and collection methods

A unique feature of LSAC is its use of multiple respondents. This provides a rich picture of children's lives and development, as responses can be compared between different respondents (e.g., parents and teachers) to provide an insight into children's behaviour in different contexts. The use of multiple respondents also helps to reduce the effects of respondent bias. In the first three waves of the study, data were collected from:

  • parents of the study child:
  • the primary parent (not necessarily a biological parent) (Parent 1) - defined as the person who knows most about the child;
  • the secondary parent (not necessarily a biological parent) (Parent 2); and
  • a parent living elsewhere (PLE) - a parent who lives apart from the child but who has contact with the child);
  • the study child;
  • carers/teachers (depending on child's age); and
  • interviewer observations.

In the first three waves of the study, the primary respondent was the child's primary carer. In the majority of cases, this was the child's biological mother, but may also have been someone else who knew the most about the child.

A variety of data collection methods have been used in the study, including:

  • face-to-face interviews;
  • self-complete questionnaires:
  • during interview:
    • on paper;
    • by computer-assisted interview (CAI); and
    • by computed-assisted self-interview (CASI);
    • leave-behind (paper); and
    • mail-out;
  • physical measurements of the child, including height, weight, girth, body fat, blood pressure;
  • time use diaries;
  • computer-assisted telephone interviews; and
  • linked administrative data (e.g., Medicare).

The interviews and questionnaires include validated scales appropriate to the children's ages.

Sampling and survey design

The sampling unit for LSAC is the study child. The sampling frame for the study was the Medicare Australia (formerly the Health Insurance Commission) enrolments database, which is the most comprehensive database of Australia's population, particularly of young children. In 2004, approximately 18,800 children were sampled from this database, using a two-stage clustered design. In the first stage, 311 postcodes were randomly selected (very remote postcodes were excluded due to the high cost of collecting data from these areas). In the second stage, children were randomly selected within each postcode, with the two cohorts sampled from the same postcodes. A process of stratification was used to ensure that the numbers of children selected were roughly proportionate to the total numbers of children within each state/territory, and within the capital city statistical districts and the rest of each state. The method of postcode selection took into account the number of children in the postcode; hence, all the potential participants in the study Australia-wide had an approximately equal chance of selection (about one in 25).1

Response rates

The 18,800 families selected were then invited to participate in the study. Of these, 54% of families agreed to take part in the study (57% of B cohort families and 50% of K cohort families). About 35% of families refused to participate (33% of B cohort families and 38% of K cohort families), and 11% of families could not be contacted (e.g., because the address was out of date, or only a post office box address was provided) (10% of B cohort families and 12% of K cohort families).

This resulted in a nationally representative sample of 5,107 0-1 year olds and 4,983 4-5 year olds who were Australian citizens or permanent residents. Table 1.2 presents the response rates for each of the three waves2.

Table 1.2 Response rates, B and K cohorts, Waves 1-3
  Wave 1 Wave 2 Wave 3
B cohort
Number 5,107 4,606 4,386
Response rate of Wave 1 100% 90.2% 85.9%
Response rate of available sample a - 91.2% 88.2%
K cohort
Number 4,983 4,464 4,332
Response rate of Wave 1 100% 89.6% 86.9%
Response rate of available sample a - 90.9% 89.7%
Total
Number 10,090 9,070 8,718
Response rate of Wave 1 100% 89.9% 86.4%
Response rate of available sample a - 91.1% 89.0%

Note: a The available sample excludes those families who had opted out of the study between waves.

1.2 Analyses presented in this report

This report includes data from the first three waves of the study. Analyses for the two cohorts (B and K) are presented separately throughout this report.

Given the breadth and depth of topics included in the study, chapters in this report do not necessarily use data from all three waves and/or cohorts. For example, under the Education theme, this report focuses on the first two waves of the study, looking at family child care arrangements. Further examination of later education will be continued in future reports.

Two general approaches are taken to the analyses in this report:

  • comparisons between certain subpopulation groups (introduced in Chapter 2) on the various aspects of children's environments and development - for example, comparison of parenting behaviours for mothers of different ages; and
  • examination of trends across waves (as children get older) - for example, examination of how patterns of child care change as children get older; or examination of individual transitions into and out of disadvantaged neighbourhoods between waves.

Weighting and survey analysis

Sample weights (for the study children) are produced for the study dataset in order to reduce the impact of bias in sample selection and participant non-response (Misson & Sipthorp, 2007; Sipthorp & Misson, 2009; Soloff, Lawrence, & Johnstone, 2005; Soloff, Lawrence, Misson, & Johnstone, 2006). This gives greater weight to population groups that are under-represented in the sample, and less weight to groups that are over-represented in the sample. Weighting therefore ensures that the study sample more accurately represents the sampled population.

These sample weights are used in analyses presented throughout this report. Cross-sectional or longitudinal weights are used when examining data from more than one wave. Analysis was conducted using Stata¬ģ svy (survey) commands, which take into account the clusters and strata used in the study design when producing measures of the reliability of estimates.

1.3 Notes

  • Information was collected from the children's primary and secondary parents (Parent 1 and Parent 2 respectively). The majority of primary parents were mothers (i.e., at all waves, more than 96% of the Parent 1 group were women) and the majority of secondary parents were fathers. In some chapters, data collected from the Parent 1 group are reported for mothers only, and data from the Parent 2 group are reported for fathers only.
  • Some chapters compare responses to particular questions between waves. In some cases, these questions were collected using different methods in different waves (e.g., by interview in one wave and by self-complete in another).
  • Unless specifically noted, all references to the child's "household" or "family" are to those of their primary parent (Parent 1), and do not include any other household or family they may have with a parent living elsewhere. Similarly, references to "parents" is to Parent 1 and Parent 2, not to parents living elsewhere.
  • Statistics are rounded to one decimal place, so totals may not sum to 100%.

1.4 Further reading

  • Australian Institute of Family Studies. (2009). Longitudinal Study of Australian Children data user guide. Melbourne: AIFS.
  • Gray, M., & Smart, D. (2008). Growing Up in Australia: The Longitudinal Study of Australian Children is now walking and talking. Family Matters, 79, 5-13.
  • Gray, M., & Smart, D. (2009). Growing Up in Australia: The Longitudinal Study of Australian Children: A valuable new data source for economists. Australian Economic Review, 42(3), 367-376.
  • Sanson, A. (2003). Growing Up in Australia: The first 12 months of a landmark study. Family Matters, 64, 40-47.
  • Sanson, A., Nicholson, J., Ungerer, J., Zubrick, S. R., & Wilson, K. (2002). Introducing the Longitudinal Study of Australian Children (Discussion Paper No. 1). Melbourne: Australian Institute of Family Studies.
  • Soloff, C., Sanson, A., Millward, C., & Consortium Advisory Group. (2003). Proposed study design and Wave 1 data collection (Discussion Paper No. 2). Melbourne: Australian Institute of Family Studies.

1.5 References

  • Department of Families, Housing, Community Services and Indigenous Affairs LSAC Team. (2009). Longitudinal Study of Australian Children: Key research questions. Melbourne: Australian Institute of Family Studies. Retrieved from <www.growingupinaustralia.gov.au/pubs/reports/krq2009/KeyResearchQuestionsJuly09.pdf>.
  • Misson, S., & Sipthorp, M. (2007). Wave 2 weighting and non-response (Technical Paper No. 5). Melbourne: Australian Institute of Family Studies.
  • Sipthorp, M., & Misson, S. (2009). Wave 3 weighting and non-response (Technical Paper No. 6). Melbourne: Australian Institute of Family Studies.
  • Soloff, C., Lawrence, D., & Johnstone, R. (2005). LSAC sample design (Technical Paper No. 1). Melbourne: Australian Institute of Family Studies.
  • Soloff, C., Lawrence, D., Misson, S., & Johnstone, R. (2006). Wave 1 weighting and non-response. Melbourne: Australian Institute of Family Studies.

Footnote(s)

1 See Soloff, Lawrence, & Johnstone (2005) for more information about the study design.

2 The sample size reported in analyses using more than one wave may be lower than shown in Table 1.2 because it includes only those responding to all waves. (Note that some of the families responding in Wave 3 did not respond in Wave 2.)

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